Both, systems used for wireless communication such as Long Term Evolution (LTE) and 5th generation (5G), and systems used for cable communication such as cable television networks, are radio systems in that they transmit and receive signals in the form of electromagnetic waves in the radio frequency (RF) range of approximately 3 kiloHertz (kHz) to 300 gigaHertz (GHz). In both of these types of systems a power amplifier that is used to amplify RF signals prior to transmission is a crucial component.
Power amplifiers can generate amplified RF signals that include nonlinear distortions. The response of power amplifiers with nonlinear distortions can result in reduced modulation accuracy (e.g., reduced error vector magnitude (EVM)) and/or out of band emissions. Accordingly, communication systems have stringent specifications on power amplifier linearity.
Digital predistortion (DPD) can be applied to enhance linearity of a power amplifier. Typically, DPD involves applying, in the digital domain, predistortion to a signal to be provided as an input to a power amplifier to reduce and/or cancel distortion that is expected to be caused by the power amplifier. The predistortion can be characterized by a power amplifier model. The power amplifier model can be updated based on the feedback from the power amplifier (i.e., based on the output of the power amplifier). The more accurate a power amplifier model is in terms of predicting the distortions that the power amplifier will introduce, the more effective the predistortion of an input to the power amplifier will be in terms of reducing the effects of the distortion caused by the amplifier.
Obtaining an accurate power amplifier model that may be used to perform DPD is not trivial and further improvements would be desirable.